Flotation process for concentrating oxides of iron



Patented Oct. 15, 1940 V UNITED STATES norarron raocnss roa ooncsnm'rmo oxmns or more James Emory Kirby, Wilmington, and Joseph- Lincoln Gillson, Holly Oak, Del., assilnors to, E. I. du Pont de Ncmours & Company, Wilmington, DeL, a corporation of Delaware 7 No Drawing. Application mm 14; 19:1, Serial No. 189,070

Claims. (01.209-166) This invention relates to an improved process for the concentration of ores, more particularly it relates to a froth flotation process employing cation active flotation agents, still more particu- 5 larly it relates to a process for separating oxides of iron from natural ores and mineral mixtures employing as a cationic flotation agent a higher aliphatic hydrocarbon substituted betain'e.

This invention has as an object the developi0 ment of an improved flotation process for the concentration of natural non-magnetic oxides of iron from ores containing them in the presence of siliceous gangue. A further object is the provision of an improved flotation process for the purification of natural oxide minerals of mm. A still further object is to provide a flotation process for concentrating natural oxide minerals of iron which does not require close control of the hydrogen ion concentration of the ore pulp.

20 Other objects include the development of a flotation process for separating oxides of iron from siliceous gangue which does not require the presence of additional agents such as activators, depressants, etc., commonly employed in prior art 28 processes for the flotation of iron oxide minerals. Still other objects include the development of a flotation process which will have greater selectivity in separating iron oxides from siliceous gangue' and thereby effect greater economies.

so Other objects will appear hereinafter.

The above and other objects appearing hereinafter are accomplished by the following invention which comprises adding to a pulp containing oxides of iron a cation-active flotation agent,

more particularly higher aliphatic hydrocarbon substituted betaines and subjecting the same to a flotation operation. If necessary, an additional frothing agent may be added. The gangue concentrates in the froth layer and leaves the flota- 49 tion cell as an over-flow while the iron oxide concentrate remains in the cell as an underflow or tailing product. The flotation agents forming a part of this invention are water-soluble and contain a high molecular weight hydrophobic 45 group. When dissolved in water these flotation agents ionize, the hydrophobic group being a part of the positive ion or cation; for this reason we term the reagents of our invention cation-active flotation agen I 50 We have found that the two most common oxide minerals of iron, hematite and limonite are practically unaffected by the cation-active flotatiton agents of this invention and are not lifted intoa flotation froth if these reagents are used 55 in the flotation process. The siliceous gangue which was predominantly quartz.

usually associated with such minerals, such as quartz and other siliceous materials, however, are selectively lifted into the froth and leave the cell as an overflow.

The invention will be further illustrated but a is not intended to be limited by the following examples:

Example I A sample of low-grade hematite ore was obtained from a mine located at Iron River, Michigan. In addition to hematite, the ore also contained a small amount of limonite and gangue The ore forms a substantial amount of nearly colloidal slime, when finely ground; for this reason it is desirable to remove most of the slime prior to'flotation,

One thousand two hundred (1200) grams of minus -mesh ore was ground for one hour in a one-gallon laboratory rod mill in the presence of 2 liters of water, 5 cc. of 40% sodium silicate solution and 3040 grams of inch steel rods. The ground charge was substantially freed from slime by repeated settling in buckets. The deslimed slurry was split into eight portions, each containing about 125 grams of ore.

One of the small charges of ground, de-siimed ore was washed into a small laboratory flotation cell ofthe type described by Gates and Jacobson 3 (Eng. Mining J. 119, 771 (1925)) and 10 cc. of a C-hexadecyl betaine hydrochloride solution containing 0.003 gram of reagent per cubic centimeter added. One drop (0.0086 g.) of an oxy= genated organic compound boiling from 147 to 157 C. at atmospheric pressure was added to induce frothing. This frothing agent was one of the branched chain, oxygenated organic compounds prepared by the catalytic hydrogenation of carbon oxides under elevated temperatures on and pressures as described in United States Patents 1,844,129; 1,844,857; and 1,939,708. Since this frothing agent is employed in several of the examples which. follow, it is designated frothing agent 2 for convenience.

With the addition of frothing agent b a heavily loaded, intensely fiocculated froth was produced and was collected 6 minutes. The product remaining in the tailing water was very dark brown in color. The tailings were removed from the cell, filtered, dried, weighed, and analyzed. The froth was returned to the cell, one drop of frothing agent b added and the product refloated. In this way a second tailing of high color.

iron content was produced. Since the material carried .out by the froth in our process is predominantly gangue, we prefer not to call it the Example II A sample of Mesabi range iron ore washer tailings was received as a mass of finely ground ore containing about 20% of water. The ore was, as received, about 95% minus 100-mesh and 76% minus ZOO-mesh. It was further ground to about 85% minus ZOO-mesh in a laboratory rod mill and deslimed prior to use in flotation tests.

Slurry containing about 109 grams of the ground deslimed ore was washed into the laboratory flotation cell described in the preceding example. Five cubic centimeters of a 0.3% solution of N-dodecylbetaine hydrochloride and one drop (0.0086 g.) of frothing agent b were added. A froth heavily loaded with intensely flocoulated minerals, light tan in color, was quickly produced. This froth was collected in a beaker during a period of 6 minutes, after which time the frothing ceased. The product remaining in the water in the flotation cell was dark brown in It was filtered, dried, weighed and analyzed for its iron content. The froth was returned to the flotation cell and refloated to produce a second underflow product of high iron content. During the course of the reflotation of the rougher froth it was necessary to add 1 cc. of the N-dodecylbetaine hydrochloride solution and one drop (0.0086 g.) of frothing agent 17. The recovery of iron (calculated as Fe) is 75%, and the quality of the rougher and cleaner underilows (expressed as per cent Fe) is 52.5 and 61.4%, respectively.

Example III A 340-pound sample of washing plant tailings obtained from a mine near Hibbing, Minnesota, was thoroughly mixed and carefullly sampled. It was found to contain 2% of moisture and 7.7% of ore coarser than l-mesh. Samples were prepared for flotation by grinding to 72% minus 200-mesh in a laboratory rod mill in presence of sodium silicate and desliming. Since only about 1.7% of slime by weight was removed it is probable that desliming was not necessary.

A charge of ground, deslimed ore was placed in the small flotation cell described in Example 1. One cubic centimeter of a 0.3% solution of C- dodecylbetaine hydrochloride and one drop (0.0086 gram) of frothing agent b were added. A heavily loaded, brownish colored froth was produced and was collected during a period of s minutes. The tailing or underflow product was dark brown in color. The froth portion was cleaned by a reflotation as in the preceding examples.

In addition to the agents of the examples, "we have found that any long chain aliphatic hydrocarbon N- or C-substituted betaine in which the aliphatic chain contains from 8 to 18 carbon atoms may be used. These betaine compounds apparently have the following formula, although there is some evidence in favor of their being noncyclic compounds.

om cm 11 11-03;- o-n wherein one of the We is a long chain aliphatic hydrocarbon radical and the other R hydrogen. The preparation of these compounds and specific examples'ot related compounds useful in this invention are given in Downing and Johnson application, Serial No. 13,664 U. 8. Patent No. 2,129,264. Useful compounds belonging to this class include betaines having a long aliphatic chain attached either to the nitrogen atom or to the carbon atom adiacent to the carbonyl group. Examples of such betaines are N-dodecyl betaine, N-cetyl betaine, N-decyl betaine, C-dodecyl betaine, C-octadecyl betaine, etc.

The betaines are particularly effective if used in the presence of small amounts of mineral or organic acids and this observation may furnish a clue to their manner of action. It is possible that the beta-ine ring tends to open by addition of acid and the resulting product tends to ionize yielding a surface active cation.

The amount of the higher aliphatic hydrocarbon substituted betaine flotation reagent required to produce the above effects varies somewhat with the reagent chosen and the particular ore being treated. In general, the amount needed will be between 0.05 and 2.0 pounds per ton of ore, but in some cases somewhat smaller or larger quantitles may be required. Some of the reagents produce-sufficient frothing so that an additional frothing agent is not required, while others have little or no frothing power. frothing power is needed, we prefer to use a material such as pine oil, cresylic acid or one of the oxygenated organic compounds described by Burdick in his U. S. Patent 1,995,915, since these frothers have no adverse effect on the selectivity of the collecting agents. Occasionally we flnd it advantageous to use mixtures of two or more ofthe higher aliphatic hydrocarbon substituted betaine reagents to produce flotation products of high quality. In carrying out a flotation process according to the teachings of this invention any of the well known types of flotation cells may be employed. The ratio of pulp solids to water may vary from about 1: 1 to 1 :6. Ordinarily a neutral pulp is used, but in some cases it may be desirable to use an alkaline or acid pulp. We have found that water glass added in quantity of about ,0.5 to about 5.0 pounds per ton of ore is often helpful in giving an increased yield of high-quality product. We have also found that certain heavy metal salts such as ferric chloride activate the siliceous minerals to a marked degree and frequently allow better separations to be made.

It will be clear from the above description that this invention is useful in the preparation of concentrates of high iron content from ores too low in iron to be of technical value. Another use is the recovery of the iron content of finely ground when greater waste pro ducts rejected by iron ore washing plants. Conversely, the process may be used to produce quartz or siliceous products of high purity and value when the principal impurities are oxides of iron.

As compared to previously known methods of concentrating non-magnetic iron ores, the present process exhibits several outstanding advantages. First of all, it provides for the first time a process by which quartz and silicate minerals may be lifted into a flotation froth while 'iron oxides remain substantially unfioated.

Secondly, it permits the ready preparation of iron concentrates in a high state of purity from ores which we have been unable to concentrate by known flotation processes. 'I'hirdly, in operating this process rigid control of the pH value of the ore pulp is not necessary, while with previously known processes success has depended on maintaining the pH value within very narrow limits.

While we have disclosed the preferred embodiments of our invention, it will be readily apparent to those skilled in the art that many variations and modifications may be made therein without departing from the spirit of the invention. Accordingly, the scope of the invention is to be limited solely by the appended claims construed as broadly as permissible in view of the prior art.

We claim:

1. The process of concentrating non-magnetic oxides of iron from pulp mixtures containing the same and siliceous gangue, which comprises adding to the pulp a small amount of a betaine compound of the general formula wherein one of the R's is a long chain aliphatic hydrocarbon radical of 8 to 18 carbon atoms and the other R is hydrogen.

2. The process of claim 1 in which the pulp is maintained in an acid condition.

3. A process as set forth in claim 1 wherein the ore treated is hematite.

4. A process as set forth in claim 1 wherein the ore treated is limonite.

5. A process as set forth in claim 1 wherein one of the R's is dodecyl and the other hydrogen.

JAMES EMORY KIRBY. JOSEPH LINCOLN GILLSON. 

